1. Field of the Invention
The invention lies in the field of processing technology, in particular in packaging technology, and relates to a device according to the preamble of the independent patent claim. The device serves for processing flat objects which are conveyed one after another in a continuous manner, or a likewise continuously conveyed, quasi endless material web, wherein a tool acts on each object or on the material web at defined, in particular regular distances, for the processing, and wherein the tool at least during its action on the object or on the material web, is moved with the object or the material web in a manner such that as much as possible, no relative movement parallel to the conveyor direction exists between the tool and the object or the material web. The device in particular serves for the finish packaging of flat objects which are conveyed one after another in a continuous manner, in particular printed products which are tucked into a film web, by way of transversely welding (sealing) the film web between consecutive objects, and severing it as the case may be.
2. Description of Related Art
The mentioned transverse welding and severing of the film web is carried out according to the state of the art, for example with a pair of cooperating, synchronously driven tools (welding bar and counter-tool) which extend transversely to the conveyor direction and parallel to the width of the film web, of which one acts on the film web from the above, and one on the film web from below. For this, the two cooperating tools rotate in the opposite direction and synchronously, in a manner such that when they are directed against one another, they may weld and separate the film web. By way of a resilient mounting of the tools and by way of a speed of the tools which is adapted to the conveyor speed, one ensures that a sufficient time interval is available for the welding and separation, during which the relative speed between the distal ends of the tools and the film web is sufficiently small for a welding and separation with no problems. The rotating tools therefore during their action on the film web, are moved at a speed, which is adapted to the conveyor speed of the film web. During their further movement, which after the welding and separation brings them back to the starting point for a further welding and separation, their speed may usually be set in a manner such that the distances of the action on the film web, thus the format of the packages to be created, may be varied. It is also known to stop the rotating movement of the tools, or to suppress their action on the film web with a part of their rotations, when the distances between the transverse weldings to be created, are too large. It is also suggested to provide several pairs of tools, in order to be able to also realise smaller distances between the transverse weldings, wherein all tools revolve synchronously and are distanced regularly to one another.
A device which operates according to the mentioned principle is described, for example, in the publication DE-2651131.
The devices of the mentioned type are greatly limited with respect to the length of the path which is available for the welding and separation of the film web. In other words, this means that, as the case may be, the conveyor speed must be reduced, should a longer acting time be necessary. The devices are likewise limited with regard to the variability of the distances between the transverse welding, wherein these distances, in particular, may not be infinitely small.
The firstly mentioned limitation is likewise remedied in known devices by way of the revolving path of the tools not being effected by a simple rotation (circular path), but by a superposition of a sliding movement parallel to the conveyor direction and a travel movement transverse to the conveyor direction. Such revolving paths are produced, for example, with the help of a crank drive or with a slide which is moved to and fro, on which a separately driven travel device is arranged. Such devices are described, for example, in the publications EP-0712782 or GB-1261179. The second limitation mentioned above is also applied to these devices.
A device for welding a material web with two part devices is known from EP-A 1 362 790. The part devices which are arranged mirror-symmetrically to the material web or its conveyor surface, in each case include two tools, which are resiliently fastened on spokes which are rotatable about a centre and, thus, are moved along a circular revolving path. In the processing region, in each case, a tool of one part device and a counter-tool of the other part device meet one another in a resilient manner, so that a certain processing pressure is exerted, and the revolving path of the actual tools flattens under pressure. The revolving path would be purely circular without a counter-pressure by way of a counter-tool or a rigid conveyor surface. A similar device with tools arranged on a wheel is known from WO00/35757.
These known devices have the advantage that the movement path of the tools, at least in the processing region, is directed largely parallel to the material web or to the objects to be processed, although the tool is moved in a very simple manner along a circular path, specifically by way of it being fastened on a rigid body which is rotatable about an axis, e.g. spokes or on a drive wheel. The straight path in the processing region has advantages, in particular when welding, since the time interval which is available for the processing is increased compared to an only point-like contact. However, one has to accept a relatively large force effect on the tools and counter-tools or the objects or their conveyor surface. This size of this force depends on the position along the movement path, and it is therefore almost always larger than that force which would be necessary for the actual processing. This may lead to quite a large wear of the tools and/or their bearings. With these examples, no defined processing whatsoever is possible without a counter-pressure by a conveyor surface or a counter-tool.